Design,Preparation And Performance Studies Of Phosphors For Full Spectrum LEDs

With the increase in global warming and environmental degradation,as well as the reduction of energy reserves,various technologies and areas related to environmental protection and energy conservation are already the most important topics of interest for society as a whole.According to incomplete statistics,lighting and displays account for more than 30%of the world's electricity consumption.The reasons for this problem is the high energy loss of conventional fluorescent lamps due to their high operating temperatures.To improve this situation,white light-emitting diodes(W-LEDs)have replaced ordinary incandescent lamps as the most promising solid-state light source.This is due to the low energy costs,environmental friendliness,small size and long duration of white LEDs.In the manufacturing process of white LEDs,phosphors occupy a very important position.The phosphor can directly influence the relevant colour temperature and colour rendering index of the LED,while the different light-emitting wavelengths of the phosphor also directly affect the design scheme of the w-LED.This thesis therefore focuses on phosphors that can be used in full spectrum LEDs,with the following experimental results.(1)A series of SrGe₄O₉:Bi³⁺,Mn⁴⁺phosphors were effectively prepared by co-precipitation method.The crystal structures of the samples were decided by X-ray diffraction and GASA refinement.The Ge2-O octahedra are nested in a six-membered ring with Sr-O octahedra and the Ge4-O octahedra are distributed in a square triangle,which facilitates the rigidity of the crystal.The crystal field is altered by Bi³⁺doping and the UV excitation is switched to the blue region due to crystal vibrations,symmetry perturbations and crystal defects.Under blue light excitation,the phosphor emits bright red light,and the red emission half-height width is only 19nm.(2)SrGe₄O₉:Bi³⁺,Mn⁴⁺has broadband excitation in the blue region.The submicron grain size prepared by co-precipitation helps us to further use it in the field of micro-LED.Under cathode-ray excitation,it has excellent cathode-luminescence(CL)properties and anti-aging properties.Sr Ge₄O₉:Bi³⁺,Mn⁴⁺with blue chips and yellow phosphors to produce white LEDs with low colour temperature and high colour rendering index?(3)In this paper,a new cyanoluminescent KBaScSi₂O₇:Ce³⁺phosphor with a scandium silicon polycyclic structure has been synthesized by a solid-phase method.One of the proposed design criteria for developing phosphors is a structure-derived strategy.By replacing Ba in KSr Sc Si₂O₇ with Ba,we succeeded in obtaining KBa Sc Si₂O₇,and this corresponding substitution provides a broader idea for the search of new phosphors.It can be matched to near-ultraviolet chips at 365nm excitation to emit bright cyan light,which not only compensates for the cyan cavity of white LEDs,but also gives high performance white LEDs with only two phosphors.In addition,the CL performance shows that KBSSO:0.10Ce³⁺has a high saturation current and voltage with good colour stability at low voltage conditions.These results indicate that KBa Sc Si₂O₇:Ce³⁺phosphor is a promising material for LED and FED applications.